Games And Entity Systems

Last week I delved into Ash – an ActionScript Entity System by Richard Lord: https://github.com/richardlord/Ash I built this little shooter: http://www.boyblack.net/proto/hunted/TopDown.html (note: something is broken with Stage3D and Chrome on Mac OSX, at least on my machine. Try it in Firefox or Safari if it doesn’t work for you, and drop me a comment).

What’s That Then?

Entity Systems offer an approach to object design that fits well with games, where requirements and behaviours need to be tweaked or swapped out constantly. Traditional object oriented design falls over a little bit in that environment. In an application (as opposed to a game), objects and collaborations are usually clearly defined and do not change after startup. Objects play specific roles, and for the most part, those roles don’t change much. In a game, however, the behaviours of “actors” within the system can change significantly during gameplay. An enemy may be stunned, for a period, losing the ability to attack. The hero may pick up a weapon, become invincible, or learn to fly. Time may slow down, speed up, or change direction. Class inheritance is obviously not a good choice here (it rarely is anyway). But actually, many object oriented design approaches are at odds with these requirements.

Ash

Ash breaks things down into Components, Entities, Nodes and Systems.

Components

Components are simple value objects: [...]
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